Biology 代写:An Introduction To Nanoscience And Nanotechnology

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8 年前

Biology 代写 An Introduction To Nanoscience And Nanotechnology

The word nanotechnology is an umbrella term and it accommodates conventional physics, biology, chemistry, materials science and full range of engineering disciplines. Nanotechnology is an entirely new concept in manufacturing that will make most products lighter, stronger, cleaner, less expensive and more precise. Nanotechnology will profoundly affect economy and society, much as the industrial revolution has. Over the past few years, we have witnessed rapid advances in the field of nanotechnology on many fronts including materials and manufacturing, nano-electronics, medicine and healthcare, energy, biotechnology and information technology. These advances have led to the availability of an array of technologies for potential applications. Applications of nanotechnology during the next few decades could produce huge increase in computer speed and storage capacity, efficient lighting and battery storage, reduction in the cost of desalinating water, clothes that never stain and glass that never needs cleaning and therapies for different types of ailments.

Technology in the twenty first century demands the miniaturization of devices into nanometer sizes while their performance is amazingly enhanced. It is widely felt that nanotechnology will be the next industrial revolution. The nanotechnology products, materials and their applications are still in developing stage and true revolution is years away, it can be a few or many years. This technology aims tinier and faster instead of bigger and slower. Thus, nanotechnology provides access to the world of the smallest things. While the benefits are almost limitless, they will be realized only if the adverse effects of nanotechnology are studied and managed.

1.1 Definition

The "nano" in nanotechnology comes from the Greek word "nanos" which means dwarf, refers to a reduction of size by 10-9 m. A nanometer (nm) equals 10-9 meter. To create a sense of nano scaled objects, one human hair is about 80,000 nanometers thick; a head of a pin is about a million nanometers wide; an atom is about 1 nm wide; a DNA molecule is about 2.5 nm wide and a red blood cell is about 5,000 nm in diameter. A nanoelement can be compared to a basketball, like a basketball to the size of the earth. Figure 1.1 illustrates the differences in scale that ranges from human all the way down to one atom. The figure also shows appropriate tools and models for the study of objects at various sizes. Atoms are the building blocks of materials and the properties of the materials can be tuned by the arrangement of atoms. Only through the use of powerful microscopes, scientists can 'see' and manipulate nano-sized particles. It is appropriate to name the nanometer scale 'the Feynman (Ï† nman) scale' after Feynman's great contributions to nanotechnology.

1 Feynman [Ï†] = 1 Nanometer [nm] = 10-9 meter =10-3 Micron [Î¼] =10 Angstroms [Å]

Nanoscience involves researches to discover new behaviours and properties of materials with dimensions at nanoscale, which ranges roughly from 1 to 100 nanometers. Nanotechnology is the research and development of materials, devices and systems by controlling shape and size at the nanometer scale with at least one novel property. The United States National Science Foundation [NSF] defines nanoscience or nanotechnology as studies that deal with materials and systems having the following key properties: (i) Dimension - at least one dimension from 1 to 100 nanometers, (ii) Process - designed with methodologies that shows fundamental control over the physical and chemical attributes of molecular-scale structures, and (iii) Building block property - they can be combined to form larger structures. The national nanotechnology initiative of NSF defines nanotechnology as 'the understanding and control of matter at dimensions of roughly 1 to 100 nanometers, where unique phenomena enable novel applications'. In short, nanotechnology is the ability to build micro and macro materials and products with atomic precision.

1.2 The Significance of the Nanoscale

The promise and essence of the nanoscale science and technology is based on the fact that materials at the nanoscale have properties (i.e. chemical, electrical, magnetic, mechanical and optical) quite different from the bulk materials. Some of such properties are intermediate between properties of the smallest elements from which they can be composed of and those of the macroscopic materials. Compared to bulk materials, nanoparticles possess enhanced performance properties when they are used in similar applications. Surface morphology, surface to volume ratio and electronic properties of materials could change appreciably due to particle size changes. Composites made from nanoparticles of ceramics or metals can suddenly become much stronger than that predicted by existing materials science models. For example, metals with a so called grain size of around 10 nanometers are as much as seven times harder and tougher than their ordinary counterparts with grain sizes in the hundreds of nanometers.

Fig. 1.1: Scale of things

Nanoscale is a magical point on the dimensional scale. Structures in nanoscale (called nanostructures) are considered as the borderline of the smallest of man made devices and the largest molecules of living systems. The ability to control and manipulate nanostructures will make it possible to exploit new physical, biological and chemical properties of systems. There are many specific reasons why nanoscale has become so important, some of which are as the following:

(i) The quantum mechanical effects come into play at very small dimensions. By designing materials at the nanoscale, it is possible to vary the fundamental properties of materials, such as electrical, optical, mechanical and magnetic without changing their chemical composition.

(ii) Nanodevices with bio-recognition properties provide tools at nanoscale, which offers a tremendous opportunity to study biochemical processes and to manipulate living cells at single molecule level. The synergetic future of nanotechnologies hold great promise for further advancement in tissue engineering, prostheses, pharmacogenomics, surgery and general medicine.

Nanoscale components have very high surface to volume ratio, making them ideal for use in composite materials, reacting systems, drug delivery and chemical energy storage. Since atom is very close to the surface or interface, behaviour of atoms at these higher-energy sites have a significant influence on the properties of the material. For example, the reactivity of a metal catalyst particle generally increases appreciably as its size is reduced. It is interesting that macroscopic gold is chemically inert, whereas at nanoscales gold becomes extremely reactive and catalytic, and even melts at a lower temperature. The larger surface area allows more chemicals to interact with the catalyst simultaneously, which makes the catalyst more effective.

Macroscopic systems made up of nanostructures can have much higher density than those made up of microstructures. They can also be better conductors of electricity. This can result in new electronic device concepts, smaller and faster circuits, more sophisticated functions and greatly reduced power consumption.

The new generations of scientific tools that operate in nanoscale enable to collect data and to manipulate atoms and molecules on a very small scale. With these tools, it is found that many familiar materials act differently and have different characteristics and properties when they are in nanoscale quantities. Moreover, materials at the nanoscale can exhibit surprising characteristics that are not seen at large scales. For instance:

Carbon in the form of graphite (like pencil lead) is soft and malleable; at the nano-scale, carbon can be stronger than steel and is six times lighter. Also, carbon atoms in the form of a nanotube exhibit tensile strength 100 times than that of steel.

Collections of gold particles can appear orange, purple, red or greenish, depending upon the specific size of the particles making up the sample.

Zinc oxide is usually white and opaque; however, at the nano-scale it becomes transparent.

Aluminum can spontaneously combust at the nano-scale and could be used in rocket fuel.

Nano-scale copper becomes a highly elastic metal at room temperature. It can be stretch up to 50 times its original length without breaking.

Researchers hope to imitate nature's secrets of building from the nanoscale, to create processes and machinery. They have already copied the nanostructure of lotus leaves to create water repellent surfaces, being used to make stain free clothing and materials. Human bodies and those of all animals use natural nanoscale materials, such as proteins and other molecules, to control many systems and processes in it. A typical protein, haemoglobin, which carries oxygen through the bloodstream, is 5 nanometers in diameter. That is, many important functions of living organisms take place at the nanoscale.

1.3 History of Nanotechnology

Humans have unwittingly employed nanotechnology for thousands of years, but it is not clear when they first began to use the advantage of nanophase materials. In the fourth century Roman glass workers were fabricating glasses containing nano metals. A cup, called Lycurgus cup (depicts the death of King Lycurgus) made during this period is exhibited at the British Museum in London. This is made from soda lime glass containing silver and gold nanoparticles. The colour of the cup changes from green to red when a source of light is placed inside it. The beautiful colours of the windows of medieval churches are also due to the presence of metal nanoparticles in the glass. During the 10th century, nanoscale gold was used in stained glass and ceramics.

In 1661, Irish chemist Robert Boyle questioned Aristotle's belief that matter is composed of earth, fire, water and air. He suggested that tiny particles of matter combine in various ways to form corpuscles. Michael Faraday published a paper in the Philosophical Transactions of the Royal Society in 1857, which explained how metal particles affect the colour of glass windows of churches. In German journal Annalen der Physik (1908), Gustav Mie reported an explanation of the dependence of the colour of the glasses on metal size. James Clerk Maxwell in 1867 mentioned some of the distinguishing concepts in nanotechnology and proposed a tiny entity known as "Maxwell's Demon". He also produced the first colour photograph that depends on production of silver nanoparticles sensitive to light in 1861.

Chemical catalysis is an example of "old nanotechnology". Today, catalysts speed up thousands of chemical transformations like those that convert crude oil into gasoline, small organic chemicals into life-saving drugs and polymers, and cheap graphite into synthetic diamond for making industrial cutting tools. Most catalysts were discovered by trial and error - by "shaking and baking" metals and ceramics, and then seeing how the result affects the reactions and their products.

Scientists have been studying and working with nanoparticles for centuries, but the effectiveness of their work has been hampered by their inability to see the structure of nanoparticles. The development of microscopes capable of displaying particles as small as atoms has allowed scientists to see what they are working with. The first observations and size measurements of nano-particles were made during first decade of 20th century by Richard Adolf Zsigmondy. He made detailed study of gold sols and other nanomaterials with sizes down to 10 nm and less. He used ultramicroscope that employs dark field method for seeing particles with sizes much less than wavelength of light. Zsigmondy was the first who used nanometer explicitly for characterizing particle size. He determined it as 1/1,000,000 of millimeter. He developed a first system classification based on particle size in nanometer range. There have been many significant developments during 20th century in characterizing nanomaterials and related phenomena, belonging to the field of interface and colloid science. In the 1920s, Irving Langmuir and Katharine B. Blodgett introduced the concept of a monolayer, a layer of material one molecule thick. Langmuir won Nobel Prize in chemistry for his work.

The concept of controlling matter at the atomic level-which is at the heart of nanotechnology's promise-was first publicly articulated in 1959 by physicist Richard P. Feynman in his speech entitled, "There's Plenty of Room at the Bottom - An Invitation to Enter a New Field of Physics." He delivered this lecture at the annual meeting of the American Physical Society at the California Institute of Technology, Pasadena, CA, on 29th December, 1959. He envisioned the possibility and potential of nanotechnology. His lecture was published in the February (1960) issue of Engineering & Science quarterly magazine of California Institute of Technology.

"A biological system can be exceedingly small. Many of the cells are very tiny, but they are very active; they manufacture various substances; they walk around; they wiggle; and they do all kinds of marvelous things - all on a very small scale. Also, they store information. Consider the possibility that we too can make a thing very small which does what we want - that we can manufacture an object that maneuvers at that level."

(Richard P. Feynman, 1959)

Feynman in his talk described how the laws of nature do not limit our ability to work at the molecular level, atom by atom. It is important to note that almost all of the ideas presented in Feynman's lecture and even more, are now under intensive research by numerous nanotechnology investigators all over the world. In his lecture Feynman challenged the scientific community and set a monetary reward to demonstrate experiments in support of miniaturizations. Feynman proposed radical ideas about miniaturizing printed matter, circuits, and machines. "There's no question that there is enough room on the head of a pin to put all of the Encyclopedia Britanica" he said. He also predicted that a library with all the world's books would fit in a pamphlet in our hand. Many of Feynman's speculations have become reality today. However, his thinking did not resonate with researchers at the time. Richard P. Feynman was awarded the Nobel Prize in physics in 1965 for his contributions to quantum electrodynamics.

The term "nanotechnology" was first coined by Japanese researcher Nario Taniguchi in 1974, to describe engineering at length scales less than a micrometer. The futurist K. Eric Drexler is widely credited with popularizing the term in the mainstream. In his books, "Engines of Creation" (1986), Drexler envisioned a world in which tiny machines or "assemblers" are able to build other structures with exquisite precision by physically manipulating individual atoms. If such control is technically achievable, atom-by-atom construction of larger objects can be a whole new way of making materials and will have the capacity to usher in a second industrial revolution with even more profound societal impacts than the first one.

Ralph Landauer (1957), a theoretical physicist working for IBM presented his ideas on nanoscale electronics and recognized the importance of quantum mechanical effects on such devices. Molecular beam epitaxy, invented by Alfred Cho and John Arthur at Bell Labs in 1968, enabled the controlled deposition of single atomic layers. In 1981Â Gerd BinnigÂ andÂ Heinrich RohrerÂ developed theÂ scanning tunneling microscopeÂ atÂ IBM's laboratories in Switzerland. This tool enables scientists to image the position of individual atoms on surfaces. For this work Binnig and Rohrer were awarded Nobel PrizeÂ in 1986. In 1985, Robert F. Curl Jr., Harold W. Kroto and Richard E. Smalley discovered buckminsterfullerence (buckyballs) which are soccer ball shaped molecules made up of carbon. Buckyball is the third known form of pure carbon after diamond and graphite. These three scientists were awarded Nobel Prize in Chemistry (1996). Sumio Iijima working for NEC Corporation, Japan discovered carbon nanotubes in 1991, while researching buckyballs using an electron microscope.

Feynman's challenge for miniaturization and his unerringly accurate forecast was met forty years later (1999) by a team of scientists using a nanotechnology tool called Atomic Force Microscope (AFM) to perform Dip Pen Nanolithography (DPN). Some of the important achievements which Feynman mentioned in his 1959 lecture included the manipulation of single atoms on a silicon surface, positioning single atoms with a Scanning Tunneling Microscope (STM) and the trapping of single, 3 nm in diameter, colloidal particles from solution using electrostatic methods. A few examples of nanomaterials are shown in figure 1.2.

Fig. 1.4: Examples of nanomaterials; (a) Buckyball, (b) SWNT, (c) MWNT,

(d) Diamondoid and (e) Nanoshell

1.3.1 Moore's Law

The top-down approach to microelectronics seems to be governed by exponential time dependence. In 1965, Gordon E. Moore, Director of Fairchild Semiconductor Division, was the first to note this exponential behaviour in his famous paper "Cramming more components onto integrated circuits". He made the astounding prediction that the number of transistors in a given area on a chip would double every two years for the next ten years. It has been observed that the transistor count in integrated circuits double in every two years as shown in figure 1.3. His prediction is popularly known as Moore's law. This trend has not only continued so far but it has crossed the limit of the prediction. There has been a corresponding decrease in the size of individual electronic elements, going from millimeters in the 60's to tens of nanometers (~ 25 nm) in modern circuitry. Moore's law plot of number of transistors on an integrated circuit versus year is illustrated in figure 1.3.

Moore's Law Equation:

Computer processing power in future years, Pn = Po x ï€ 2n,

where Po = computer processing power in the beginning year,

n = number of years to develop aÂ new microprocessor divided by 2.

.

Fig. 1.3: Moore's law plot of number of transistor on an IC/CPU versus year

In the last century, the transition from one technology to another has occurred several times in information industry. For example, the mechanical relay was replaced by the vacuum tube, which was then substituted by the transistor. Subsequently, the transistor gave way to the current integrated circuit.

1.4 Applications

The enhanced abilities to understand and manipulate matter at the molecular and atomic levels promise a wave of significant new technologies over the next few decades. Dramatic breakthroughs will occur in diverse areas such as medicine, communications, computing, energy, and robotics. These changes will generate large amounts of wealth and force wrenching changes in existing markets and institutions. The aim of this section is to give an overview of the significant foreseeable applications of nanotechnology. A detailed discussion of the various potential applications of nanotechnology is given in chapter 7.

1.4.1 Medicine

Nanomaterials are one of the most interesting bio-sensing materials because of their unique size and shape dependent optical properties, high surface energy and surface-to-volume ratio, and tunable surface properties. A wide variety of nanomaterials have found very useful applications in many kinds of biosensors for the diagnosis and monitoring of diseases, drug discovery, proteomics, environmental detection of biological agents and so on. Since disease is the result of physical disorder of misarranged molecules and cells, medicine at this level should be able to cure most diseases. Hence, nanotechnology has wide scope in medicine. Nanostructures such as particles and polymeric dendrimers could be designed as drug delivery systems. Assembler-based manufacturing will provide new tools for medicine, making possible molecular-scale surgery to repair and rearrange cells. Mutations in DNA could be repaired, and cancer cells, toxic chemicals, and viruses could be destroyed through use of medical nanomachines, including cell repair machines. Nanotechnology will improve health care, help to extend the life span, improve its quality, and extend human physical capabilities. Medicinal fluids containing nano robots are programmed to attack and reconstruct the molecular structure of cancer cells and viruses to make them harmless. Nanorobots could also be programmed to perform delicate surgeries. Nanotechnology will create biocompatible joint replacements that will last for entire life of the patient.

Fig. 1.4: Biosensors for detecting biomarkers of cancer: (a) Nanoscale cantilevers,

(b) Nanowire sensors.

With faster and cheaper diagnostic equipments, better diagnostic tests will be conducted. For example, DNA mapping of the newborn children may help to point out future potential problems and thereby prevent disease before it takes hold. Today most harmful side effects of treatments such as chemotherapy are a result of drug delivery methods that cannot pinpoint their intended target cells accurately. Researchers at Harvard University have been able to attach special RNA strands, measuring about 10 nm in diameter, to nanoparticles and fill the nanoparticles with a chemotherapy drug. These RNA strands are attracted to cancer cells. When the nanoparticle encounters a cancer cell it adheres to it and releases the drug into the cancer cell. This directed method of drug delivery has great potential for treating cancer patients while producing less side harmful effects than those produced by conventional chemotherapy. Figure 1.4 shows biosensors, such as nanoscale cantilevers and nanowires, for detecting biomarkers of cancer.

1.4.2 Nanoelectronics

Nanoelectronics can be used to build computer memory, using individual molecules or nanotubes to store bits of information. It has potential applications in molecular switches, molecular or nanotube transistors, nanotube flat-panel displays, nanotube integrated circuits, fast logic gates, switches, nanoscopic lasers and nanotubes as electrodes in fuel cells.

1.4.3 Batteries

With the tremendous growth in portable electronic equipments such as mobile phones, navigation devices, laptop computers, remote sensors, there is a great demand for lightweight and high-energy density batteries. Nanomaterials synthesized by sol-gel techniques are candidates for separator plates in batteries because of their aerogel structure, which can hold considerably more energy than conventional ones. Nickel-metal hydride batteries made of nanocrystalline nickel and metal hydrides are envisioned to require less frequent recharging and to last longer because of their large surface area.

1.4.4 Environmental Protection

Nanotechnology has the potential to benefit the environment through pollution treatment and remediation as any waste atoms could be recycled, since they could be kept under control. This would include improved detection and sensing, removal of the finest contaminants from air, water and soil, and creation of new industrial processes that reduce waste products and are ecofriendly. Airborne nanorobots could be programmed to rebuild the thinning ozone layer. Immense tonnage of excess carbon dioxide in the atmosphere could be economically removed air bone. One of the biggest environmental challenges that humanity faces today is clean water. The potential benefits of nanotechnology also help to remove the finest [i.e. smallest] contaminants from water and air, promoting a cleaner environment and potable water at an affordable cost. Nanoparticles of iron can be effective in the cleanup of chemicals in groundwater because they react more efficiently to those chemicals than larger iron particles.

1.4.5 Agriculture

Nanotechnology will improve agricultural yields for an increased population, provide more economical water filtration and desalination, and improve renewable energy sources, such as solar energy conversion. Nanotechnology has a significant effect in the main areas of the food industry: development of new functional materials, product development and design of methods and instrumentation for food safety and bio-security. Using nanoparticle technology, Bayer has developed an airtight plastic packaging that will keep food fresher and longer than their previous plastics. Nanotechnology will also help to modify the genetic constitution of the crop plants, thereby helping improvement of crop plants. Nanotechnology based plant disease diagnostics help to detect exact strain of virus and stage of application of some therapeutic to stop the disease.

1.4.6 Energy

Energy applications of nanotechnology include storage, conversion, manufacturing improvements by reducing materials and process rates, energy saving and enhanced renewable energy sources. Nanotechnology could help increase the efficiency of light conversion of solar cells by using nanostructures with a continuum of band gaps. Nanotechnological approaches like light-emitting diodes (LEDs) or quantum caged atoms (QCAs) could lead to a strong reduction of energy consumption for illumination. An environmental friendly form of energy is the use of fuel cells powered by hydrogen. The most prominent nanostructured material in fuel cells is the catalyst consisting of carbon supported noble metal particles with diameters of 1-5 nm. Suitable materials for hydrogen storage contain a large number of small nanosized pores. Therefore many nanostructured materials like nanotubes, zeolites or alanates are under investigation.

1.4.7 Nano products/devices

The ability to see nano-sized materials has opened up a world of possibilities in a variety of industries and scientific endeavors. As mentioned earlier, nanotechnology is essentially a set of techniques that allow manipulation of properties at a very small scale and it may help to revolutionize products everywhere, creating a vast array of new products and devices. The promise of these products and devices is tremendous. Nanotechnology can change the nature of almost every manufactured product. Because of this, nanotechnology will have more influence than the silicon integrated circuit, medical imaging, or computer-aided engineering. Amazingly, more than 1000 commercial nanomaterial-based products are available in the market.

The properties of familiar materials are being changed by manufacturers who are adding nano-sized components to conventional materials to improve performance. For example, some clothing manufacturers are making water and stain repellent clothing using nano-sized whiskers in the fabric that cause water to bead up on the surface. Companies are now manufacturing nanoparticles for use in hundreds of commercial products - from crack-resistant paints and stain-resistant clothing, to self cleaning windows and anti-graffiti coatings for walls.

Some examples of nano products/devices:

Exploiting the anti-bacterial properties of nano-scale silver, Smith & Nephew developed wound dressings (bandages) coated with silver nano-crystals designed to prevent infection. Hundreds of products incorporating nanosilver are now on the market, including sheets, towels, appliances, socks, toothbrushes, toothpastes and children's toys.

Nanoparticles of titanium dioxide (TiO2) are transparent and block ultraviolet (UV) light. Nano-scale TiO2 is now being used in sunscreens and in clear plastic food wraps for UV protection.

Nano-scale particles of hydroxyapatite have the same chemical structure as tooth enamel. Researchers at BASF are hoping to incorporate the nanoparticles in toothpaste to build enamel-like coating on teeth and to prevent bacteria from penetrating. Sangi Co. Ltd. (Japan) has been selling a toothpaste containing nano-hydroxyapatite since 1980.

Nano-Tex sells "Stain Defender" for khaki pants and other fabrics - a molecular coating that adheres to cotton fiber, forming an impenetrable barrier that causes liquids to bead and roll off.

Pilkington sells a "self-cleaning" window glass covered with a surface layer of nano-scale titanium dioxide particles. When the particles interact with UV rays from sunlight, the dirt on the surface of the glass is loosened, washing off when it rains.

BASF sells nano-scale synthetic carotenoids as a food additive in lemonade, fruit juices and margarine (carotenoids are antioxidants and can be converted to Vitamin A in the body). According to BASF, carotenoids formulated at the nano-scale are more easily absorbed by the body and also increase product shelf life.

Syngenta, the world's largest agrochemical corporation, sells two pesticide products containing nano-scale active ingredients. The company claims that the extremely small particle size prevents spray tank filters from clogging and the chemical is readily absorbed into the plant's systems and cannot be washed off by rain or irrigation.

Altair Nanotechnologies is developing a water-cleaning product for swimming pools and fishponds. It incorporates nano-scale particles of a lanthanum-based compound that absorbs phosphates from the water and prevents algae growth.

Silicon-based, disposable blood-pressure sensor chips were introduced in the early 1990s by NovaSensor for blood pressure monitoring.

A variety of biosensors are manufactured by various companies, including ACLARA, Agilent Technologies, Calipertech, and I-STAT.

1.5 Risks of Nanomaterials

Although nanotechnology has a significant impact on society, and every sector of economy, nanomaterials may pose new risks to workers, consumers, public and environment. Risks can occur anywhere nanomaterials come in contact with people, animals or environment. Key risks relate to liability, privacy, financing and safety of products. For the health arena, the most immediate concerns are likely the safe and ethical use of nanomaterials. The microscopic size of nanoparticles makes them difficult to be detected and controlled. Researchers, staff, consumers or patients may inadvertently inhale therapeutic products. The models and predictability of these molecular interactions are not yet known. Thus, precautions to avoid inhalation and emergency methods to disable the technology will be needed. Current gloves, masks, and gowns may not provide adequate protection, creating a need for new evaluation research, new protective equipment, and a calculation of the associated costs before the technology is widely used. Only a few research findings are available about the safety of nanomaterials. Researchers found that nanoparticles can provoke increased inflammatory responses and potentiate the effect of medications.

People have started to raise serious questions about the possible impact of nanomaterials on human health. The small size of nanoparticles can give them greater access to body tissues and organs than larger particulates. Animal studies have reported that some inhaled nanomaterials pass easily from the nose directly into the brain via olfactory neurons, and from lungs into the blood stream. Once nanomaterials enter the body, the larger surface area of nanomaterials per unit of mass makes them more chemically reactive than their normal-scale counterparts, and therefore more likely to interact with biological molecules. Cell studies indicate that some nanomaterials may interact with cell DNA, cause inflammation and oxidative damage, and impair cell function. Engineered modifications to nanomaterials, such as surface coatings, can alter a material's solubility, chemical activity, toxicity, and other properties, providing an opportunity to reduce the risks associated with a material early in its design. Although there is a paucity of toxicity data specific to engineered nanomaterials, the hazards of nanosize air pollutants are well documented. Particulate matter less than 10Î¼m (10,000 nm) has been linked to increased lung cancer and cardiopulmonary disease. While all particulate air pollution is hazardous, smaller inhaled particles have long been known to be more damaging to body tissues than larger particles, inducing inflammation and tissue damage. The risks are especially high among individuals with pre-existing heart and lung ailments, including asthma and chronic obstructive pulmonary disease, suggesting that millions of people with these conditions may be vulnerable to the hazards of inhaled nanomaterials. A variety of nanomaterials has the capacity to cause tissue and cellular damage by causing oxidative stress. Report shows that Bulkyballs caused oxidative damage to brain and liver cells in a study in largemouth bass. Other nanoparticles have also been shown to cause oxidative stress in skin cells and liver. Oxidative stress may also cause damage to lung tissue. These kinds of disquieting behaviours have generated an urgent need for more research about the safety of nanomaterials.

The ethical use of nanomaterials is a major area of concern for health care providers. Obviously, guidelines along with the risk possible with nanoamaterials should be created to preserve human dignity and integrity. Much of the current focus is to determine what research should be done about the risks of nanomaterials. Nanotechnologists have published five grand challenges for the safe handling of nanotechnology. They are,

develop instruments to assess exposure to engineered nanomaterials in air and water,

develop and validate methods to evaluate the toxicity of engineered nanomaterials,

develop models for predicting the potential impact of engineered nanomaterials on the environment and human health,

iv) develop robust systems for evaluating the health and environmental impacts of engineered nanomaterials over a human lifetime, and

v) develop strategic programmes that enable relevant risk-focused research.